Agriculture and Agri-Food Canada, London, Ontario, Canada.
Appl Environ Microbiol. 2013 Apr;79(7):2435-45. doi: 10.1128/AEM.03501-12. Epub 2013 Feb 1.
The detection and abundance of Escherichia coli in water is used to monitor and mandate the quality of drinking and recreational water. Distinguishing commensal waterborne E. coli isolates from those that cause diarrhea or extraintestinal disease in humans is important for quantifying human health risk. A DNA microarray was used to evaluate the distribution of virulence genes in 148 E. coli environmental isolates from a watershed in eastern Ontario, Canada, and in eight clinical isolates. Their pathogenic potential was evaluated with Caenorhabditis elegans, and the concordance between the bioassay result and the pathotype deduced by genotyping was explored. Isolates identified as potentially pathogenic on the basis of their complement of virulence genes were significantly more likely to be pathogenic to C. elegans than those determined to be potentially nonpathogenic. A number of isolates that were identified as nonpathogenic on the basis of genotyping were pathogenic in the infection assay, suggesting that genotyping did not capture all potentially pathogenic types. The detection of the adhesin-encoding genes sfaD, focA, and focG, which encode adhesins; of iroN2, which encodes a siderophore receptor; of pic, which encodes an autotransporter protein; and of b1432, which encodes a putative transposase, was significantly associated with pathogenicity in the infection assay. Overall, E. coli isolates predicted to be pathogenic on the basis of genotyping were indeed so in the C. elegans infection assay. Furthermore, the detection of C. elegans-infective environmental isolates predicted to be nonpathogenic on the basis of genotyping suggests that there are hitherto-unrecognized virulence factors or combinations thereof that are important in the establishment of infection.
水中大肠埃希氏菌的检测和丰度可用于监测和规定饮用水和娱乐用水的质量。区分肠道共生的大肠埃希氏菌分离株和引起人类腹泻或肠道外疾病的分离株对于量化人类健康风险很重要。本研究使用 DNA 微阵列评估了加拿大安大略省东部流域的 148 个环境大肠埃希氏菌分离株和 8 个临床分离株中毒力基因的分布情况。用秀丽隐杆线虫评估它们的致病潜能，并探索生物测定结果与通过基因分型推断的病原型之间的一致性。基于其毒力基因组成鉴定为具有潜在致病性的分离株比鉴定为具有潜在非致病性的分离株更有可能对秀丽隐杆线虫具有致病性。基于基因分型鉴定为非致病性的许多分离株在感染测定中具有致病性，这表明基因分型未捕获所有潜在的致病性类型。黏附素编码基因 sfaD、focA 和 focG、铁载体受体 iroN2、自转运蛋白 pic 和转座酶编码基因 b1432 的检测与感染测定中的致病性显著相关。总的来说，基于基因分型预测为致病性的大肠埃希氏菌分离株确实在秀丽隐杆线虫感染测定中具有致病性。此外，检测到的预测为基于基因分型非致病性的能感染秀丽隐杆线虫的环境分离株表明，存在迄今为止尚未认识到的重要感染建立因子或其组合。
